fix: qlc could not create temp files in docker container (#12875)

[id]

Fixes #12875

qlc uses file_sorter that puts temporary files in the working directory by default, which is not writable by emqx user since 58d0f04.

One of the consequences is that users cannot access retained messages from the dashboard, but there are likely other issues as well.

This patch fixes this by making /opt/emqx directory owned by emqx:emqx.

Release version: v/e5.6.1

Summary

PR Checklist

Please convert it to a draft if any of the following conditions are not met. Reviewers may skip over until all the items are checked:

• Added tests for the changes
• Added property-based tests for code which performs user input validation
• Changed lines covered in coverage report
• Change log has been added to changes/(ce|ee)/(feat|perf|fix|breaking)-<PR-id>.en.md files
• For internal contributor: there is a jira ticket to track this change
• Created PR to emqx-docs if documentation update is required, or link to a follow-up jira ticket
• Schema changes are backward compatible

Checklist for CI (.github/workflows) changes

• If changed package build workflow, pass this action (manual trigger)
• Change log has been added to changes/ dir for user-facing artifacts update